funkgab

So i tried to fix my headliner.. with the 3M adhesive but it just got alot worse.. now my whole headliner fell apart.. so i was forced to tape it.. (maybe it was too cold)
anyways my rear bulb was on so the battery died..
and i got the car jumped and it works fine now, but when i start the car the tachometer doesn't move until i pump the accelerator.. any ideas on how to fix this?
also i noticed that my lights flicker.. i know i have a vacuum leak, but can this be the cause of it?

AcousticplayerJ

Oh boy. Sounds like a whole host of things. First off, the wiring could be going. Usually the tach is driven electronically. So perhaps those cables are loose. You might have to take out the instrument cluster to check. There's a guide here: http://mymbonline.com/forum/viewtopi...ee8a32e2e48237 (it's for changing bulbs, but it will still help you get the cluster out).

Then, maybe you would want to have your alternator tested too. But it really sounds like a case of bad wiring to me :/

xvvvz

It sounds like the tach is just sticking to the resting needle. A common issue. If so, you would just need to remove the cluster and clean the needle.

funkgab

kinda scared i might break something in the process :/ my outside temp light is out though, and the plastic cover on the cluster is pretty dirty so that needs cleaning too so eventually im going to have to do it..

and how do i test the alternator? i have a multimeter from the 70's.. and when i tried it on the battery when the car was off, it goes to 10 - 10.5 volts, with the car on it goes to 11, 11.5.. so the alternator is still charging.. but is it losing charging power?

AcousticplayerJ

Well, hook the leads of the multimeter up to the alternator, and rev the engine. The voltage should increase. Remember, DC current comes out of the alternator, so set the multimeter to that. Also, you can rev the engine from under the hood (if you didn't know that already ) So as long as the voltage increases with increased RPMs, it should be ok. I would think maybe 14 to 15 volts would be a good output. Though I'm not sure, because alternators have internal voltage regulators. I'm trying to think back to when I rebuilt a generator for an old british car. That was a treat.

The cluster isn't too hard to take out. It does require a bit of force because it's held in by only friction. So it can be scary the first time. But I think it would be really hard to break it. It's up to you if you want to deal with that.

funkgab

hopefully it doesn't require more force than the rear mirror cause that was a pain in the ***.. and thats scary hooking up the multimeter to the alt.. where do i connect it? just to any part of it? and what revs the engine from the hood?

AcousticplayerJ

The attached picture will show you how to rev your engine... Hmm, maybe that's where that expression came from?

And yeah, you're absolutely right. I didn't realize how inaccessible the alternator is. So it's not going to be practical to hook the multimeter up to it. You could just hook the leads up to the battery terminals and have someone rev the engine for you while you do the reading. There should be an increase in voltage. If your battery is getting old (like 4+ years) it could be time to get a new one. But if your car seems to be functioning fine, electrically, then I wouldn't worry about the alternator for now. There's a warning light on the dash for the battery which will turn on if the battery drops below a certain voltage. If this happens, then the alternator is likely not outputting enough current to sustain a charge.

Good luck!

Slug-Gunner

I'm not that familiar with MB specs, but they should be consistent with most other automotive specs too. Battery voltage on a FULLY CHARGED battery should be in the 12.6-12.7 VDC range..... if an automotive battery ONLY READS 12.0 VDC IT IS IN A 'DISCHARGED CONDITION'. If your battery is over 4 years old, it is most likely readiing the end of its useful life and needs replacing. You can take it to a parts store like AutoZone or Advance Auto and they can do a "Battery Load Test" on it for your FREE OF CHARGE. This should involve them charging the battery with the tester for a few minutes first to see if it is capable of taking a 'fast charge', then once it is charged to a specified voltage, they should perform a LOAD TEST on it which will determine if it still has a USEFUL CAPACITY in it.

To test your alternator output voltage at the BATTERY TERMINALS.

1. First, TURN OFF ALL ACCESSORIES and measure the BATTERY VOLTAGE at the battery terminals - to determine it's CHARGED STATUS.
2. Start the engine and read the voltage at IDLE SPEED - IT SHOULD READ BETWEEN 13.5-14.5 VDC (depending on battery 'charge state')
3. Have someone increase engine rpm to around 1500-2000 rpm and see if alternater output increase any.

NOTE:
With a FULLY CHARGED BATTERY, a properly functioning alternator (with internal rectifier/voltage regulator system) should be having an output in the 13.7-14.2 VDC rangel, depending on WHAT ACCESSORIES MIGHT BE OPERATING.

Post the results of your testing here for evaluation.

BTW:
If you want to learn more about BATTERIES (for both automotive and electronic applications), go to the Battery University.com web site and follow the following link for info on how to use it effectively. (click here)

xvvvz

Yeah, I would suspect the batter first before the alternator. If it does turn out to be the alternator, it is very likely it is just a bad regulator. Those are $25 and you can install it yourself if you are decent with tools.

Slug-Gunner

I was in a hurry earlier when I replied and it shows in a couple of typos I made. Your indications of measuring only 10-10.5 VDC at your battery indicates that YOU MAY HAVE A DEAD CELL IN YOUR BATTERY (most likely a 'shorted' cell/sulfated). Your alternator should still be putting out a minimum of 13.5 VDC, EVEN WITH A WEAK BATTERY, but you REALLY NEED A FULLY CHARGED BATTERY TO CHECK ITS OUTPUT PROPERLY. I've known several people who have put a new alternator in their car and immediately 'burned it up' because their battery was EXTREMELY WEAK when they started their engine up.

Since you say you 'jump started' your car because your battery had discharged when you left your interior light on, if you ACCIDENTALLY REVERSED THE POLARITY ON THE BATTERY CABLE HOOK-UP (on EITHER vehicle), you may have damaged some of the electronics in your car, even the ECU/COMPUTER. EVEN A 'MOMENTARY' REVERSAL OF THE CONNECTIONS (SPARKS FLYING) CAN CAUSE THEM TO BE DAMAGED. If the 'donor' charging vehicle HAD THEIR ENGINE RUNNING when you tried to start your engine, HE MAY HAVE DAMAGED HIS ALTERNATOR TOO.

MOST ALTERNATOR SYSTEMS ARE NOT DESIGNED TO HANDLE THE CURRENT REQUIRED TO START A VEHICLE AND CHARGE A 'DEAD BATTERY' AT THE SAME TIME! The STARTING CURRENT required for a vehicle can easily EXCEED 150 AMPS - NOT MANY ALTERNATORS ARE RATED THAT HIGH.

funkgab

i always grounded the negative circuit to avoid sparks flying when jumping a car but never knew jump starting was so bad for the car.. well its been jumped twice, and i borrowed my cousin's self jumper from then on

anyways i got the starter, alternator, and battery tested for free at auto zone, they charged the battery too.. and it said health is 85%, so still good..

the thing is my dome lights and cluster still seem to dim, by making a whirling sound from the passenger side in the trunk (vacuum leak im guessing?) every time the sound comes on, the lights dim..

but after the battery died, and got jump started, the cluster dim and clock seemed to have gotten reset, same when i got my battery charged at autozone

AcousticplayerJ

Oh good. Yeah, probably a vac leak. I have the same issue when my doors lock or unlock. Just a little hissing, but no big deal.

If the lights dim, then perhaps something is drawing a lot of current. Do you have a lot of devices plugged into the cig adapter? Maybe a lot of lights on at once? Some dimming is normal. Like if you have your headlights on when you start the car, the lights will flicker and dim since the starter draws a lot of power. I really wouldn't worry too much. It's probably nothing serious.

funkgab

nothing plugged into cig outlet

xvvvz

Those little pumps are expensive so I would get that leak fixed before you burn it out.

Did the guy at autozone seem knowledgeable enough to trust his test of the battery?